1. Field of the Invention
The present invention relates to a content based image retrieving system, and more particularly, to a method for retrieving an image using multiple features per subregion of an image.
2. Background of the Related Art
An image retrieving system generally searches for a reference image by extracting certain characteristics of the images. The characteristics of images may be extracted as the images are input to an image database and the extracted characteristics are stored in the image database. Subsequently, if a user requires an image search, a similarity between respective images are determined utilizing the characteristic information of a reference image and target images stored in the database.
In one image retrieving system, an image is divided into subregions and the subregion is further divided into pixel units to represent each subregion with one regional representative color, such as an average color for all pixels. The subregion information is used to match the target images with a reference image, thereby examining the similarity. However, this method does not perform as well when a plurality of colors are present in one subregion, making it difficult to represent the subregion with one regional representative color.
In another image retrieving method, the colors of all pixels in a subregion are represented with a plurality of values, such as color histogram and the image is represented using the values as the subregion information to retrieve an image. Although this method may perform better, due to the use of the plurality of color values, a longer retrieval time is necessary. For example, when using a color histogram of nth dimension, a comparison of n elements is required.
Accordingly, an object of the present invention is to solve at least the problems and disadvantages of the related art.
An object of the present invention is to provide an efficient method for retrieving an image.
Another object of the present invention is to provide an efficient method for retrieving an image using multiple features per a subregion of an image.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purposes of the invention, as embodied and broadly described herein, the method for retrieving an image using multiple features per a subregion of an image includes (1) dividing an image into subregions, extracting a regional representative color and a confidence measure of the regional representative color for each of the subregions, and extracting at least one other characteristic of the image, (2) comparing the confidence measure of the regional representative color for an extracted subregion to a threshold value, and (3) determining a similarity between a reference image and a target image using the regional representative color if the confidence measure of the regional representative color for the subregion is higher than the threshold value, and otherwise determining a similarity between a reference image and a target image using the at least one other characteristic of the image.
In the present invention, the other characteristic of the image may be one or a combination of both the a set of main colors of subregions and a frequency of each main color, and region feature information other than the color information.